Hydrothermal synthesis and structural characterization of novel Zn-triazole-benzenedicarboxylate frameworks

Three new metal-organic coordination polymers were synthesized hydrothermally using Zn ²⁺ ion, 1,2,4-triazole, and 1,4-benzenedicarboxylic acid (BDC): Zn ₅(H ₂O) ₂(C ₂H ₂N ₃) ₄(C ₈H ₄O ₄) ₃·3.9H ₂O(1), Zn ₂-(C ₂H ₂N ₃) ₂(C ₈H ₄O ₄)Middot;2.5H ₂O ₂(2), and Zn ₄(H ₂O) ₂(C ₂H ₂N ₃) ₄(C ₈H ₄O ₄)Middot; 14H ₂O (3). Their crystal structures were determined by single-crystal X-ray diffraction. Their thermal properties were examined by thermogravimetric analysis. Structure 1 crystallizes in the monoclinic P2 ₁/n space group with a = 10.192(2) Å,b = 17.764(4) Å, c = 24.437(5) Å, β= 91.19(3)°, and V = 4423.3(15) Å ³. Structure 2 crystallizes in the triclinic P̄1 space group with a = 7.797(2) Å, b = 10.047(2) Å, c = 13.577(3) Å, α = 110.18(3)°, β= 105.46(3)°, γ = 93.90(3)°, and V = 947.0(3) Å ³. Structure 3 crystallizes in monoclinic P2 ₁/n space group with a = 13.475(3) Å, b = 26.949(5) Å, c = 13.509(3) Å, β= 95.18(3)°, and V = 4885.7(17) Å ³. In structure 1, the units of the triazole-Zn polyhedra are linked by BDC in a zigzag fashion to create the stacking of phenyl groups along the a axis. In structure 2, both triazole and BDC bridge Zn polyhedra in the (011) plane, resulting in the eight-membered channels along the a axis. In the case of structure 3, the BDC links the Zn polyhedra along the b axis to form a pillared open framework. This structure is the most porous of the compounds presented in this work.